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A161848 Primes with at least one digit appearing exactly three times in the decimal expansion. 0

%I #7 Feb 21 2019 23:15:40

%S 1117,1151,1171,1181,1511,1777,1811,1999,2111,2221,2333,2777,2999,

%T 3313,3323,3331,3343,3373,3433,3533,3733,3833,4111,4441,4447,4999,

%U 5333,5557,6661,7177,7333,7477,7577,7717,7727,7757,7877,8111,8887,8999,9199,9929

%N Primes with at least one digit appearing exactly three times in the decimal expansion.

%C Sequence is probably infinite.

%e 2333, 3313, 3833 all repeat some digit 3 three times.

%p isdgctm := proc(n,d) local dgs,a,i ; dgs := convert(n,base,10) ; a := [seq(0,j=0..9)] ;

%p for i in dgs do a := subsop(i+1=op(i+1,a)+1,a) ; od: if convert(a,set) intersect {d} <> {} then true; else false; fi; end:

%p for n from 1 to 2000 do p := ithprime(n) ; if isdgctm(p,3) then printf("%d,",p) ; fi; od: # _R. J. Mathar_, Jun 21 2009

%Y Cf. A161786, A161796.

%K nonn,base

%O 1,1

%A _Ki Punches_, Jun 20 2009

%E Edited and corrected by _R. J. Mathar_, Jun 21 2009

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Last modified July 12 11:04 EDT 2024. Contains 374244 sequences. (Running on oeis4.)